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5 - The 2003 and 2007 Wildfires in Southern California
- from Part I - Case Studies from North America
- Edited by Sarah Boulter, Griffith University, Queensland, Jean Palutikof, Griffith University, Queensland, David John Karoly, University of Melbourne, Daniela Guitart, Griffith University, Queensland
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- Natural Disasters and Adaptation to Climate Change
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- 05 October 2013
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- 14 October 2013, pp 42-52
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Contributors
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- By W. Neil Adger, Jeroen Aerts, Armando Apan, Jessica Ayers, Jon Barnett, Juan F. Barrera, Simon P. J. Batterbury, Linda C. Botterill, Sarah Boulter, Edwin Castellanos, Declan Conway, Gustavo Cruz-Bello, W. Priyan, S. Dias, Markus G. Donat, Stephen Dovers, Thomas E. Downing, Hallie Eakin, C. J. Fotheringham, Andrew W. Garcia, Marisa C. Goulden, Daniela Guitart, John Handmer, Katharine Haynes, Sam S. L. Hettiarachchi, Saleemul Huq, Jiang Tong, David John Karoly, Jon E. Keeley, Diane Keogh, David King, Zbigniew W. Kundzewicz, Timothy M. Kusky, Karine Laaidi, Alain Le Tertre, Gregor C. Leckebusch, Matthew Mason, David M. Mills, Helda Morales, Michael J. Mortimore, Colette Mortreux, Karen O’Brien, Jean Palutikof, Mathilde Pascal, Bimal K. Paul, Munshi K. Rahman, William D. Snook, Su Buda, Alexandra D. Syphard, Melanie Thomas, Madeleine C. Thomson, Uwe Ulbrich, Pier Vellinga, George Walker, Joshua Whittaker
- Edited by Sarah Boulter, Griffith University, Queensland, Jean Palutikof, Griffith University, Queensland, David John Karoly, University of Melbourne, Daniela Guitart, Griffith University, Queensland
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- Natural Disasters and Adaptation to Climate Change
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- 05 October 2013
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- 14 October 2013, pp ix-xii
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15 - Structural equation modeling and the analysis of long-term monitoring data
- Edited by Robert A. Gitzen , University of Missouri, Columbia, Joshua J. Millspaugh, University of Missouri, Columbia, Andrew B. Cooper, Simon Fraser University, British Columbia, Daniel S. Licht
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- Design and Analysis of Long-term Ecological Monitoring Studies
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- 05 July 2012
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- 07 June 2012, pp 325-358
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Summary
Introduction
The analysis of long-term monitoring data is increasingly important; not only for the discovery and documentation of changes in environmental systems, but also as an enterprise whose fruits validate the allocation of effort and scarce funds to monitoring. In simple terms, we may distinguish between the detection of change in some ecosystem attribute versus the investigation of causes and consequences associated with that change. The statistical framework known as structural equation modeling (SEM) can contribute to both detection of changes and the search for causes. This chapter summarizes some of the capabilities of SEM and shows a few ways it can be used to model temporal change. Because of its ability to test hypotheses about whether rates of change are zero or nonzero, it can be used for change detection with repeated-measures data. As more of the capabilities of SEM are presented, its capacity for evaluating causal networks is highlighted. Here is where its potential for making a unique contribution to the analysis of long-term monitoring data is revealed. Thus, one's primary motivation for using SEM with monitoring data will be to investigate hypotheses about what factors may be driving change (Box 15.1).
9 - Fire-adaptive Trait Evolution
- from Section III - Comparative Ecology, Evolution and Management
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- Fire in Mediterranean Ecosystems
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- 05 January 2012
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- 30 December 2011, pp 233-274
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Summary
Until relatively recently the importance of fire and the origin of fire-adaptive traits have received minimal attention from paleoecologists, and appreciation of this importance has varied across the different mediterranean-type climate (MTC) ecosystems. For example, Axelrod (1973) and Raven & Axelrod (1978) wrote extensive treatises on the origins of the California flora, and yet gave little or no mention to the issue of fire in the evolution of these taxa. Hopper (2009) suggests that fire has only been an incidental factor in the evolution of the Western Australian flora. These investigators have weighed climate and soils far above fire as an important evolutionary driver in these plant assemblages and have downplayed this component of community assembly (see Fig. 1.4).
Axelrod (1989) even went so far as to suggest fire was irrelevant to the evolution of California chaparral. Although he acknowledged that fire could have played a role in the spread of chaparral-like vegetation during the late Tertiary (2–10 Ma), he insisted that fire had played no significant role in the origin of “adaptive types.” In his view, “Several lines of evidence suggest that the modern fire-adapted taxa may not reflect an evolutionary response to fire. The diverse adaptations to fire probably represent features that originated without the stimulus of fire. . .” Contrary to this belief, we suggest there is sufficient reason to accept a fire origin for many fire-adaptive traits in mediterranean-type vegetation (MTV), and that fire has been a potential ecosystem process on landscapes far longer than the late Tertiary (Bowman et al. 2009; Pausas & Keeley 2009).
12 - Alien Species and Fire
- from Section III - Comparative Ecology, Evolution and Management
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- Fire in Mediterranean Ecosystems
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- 05 January 2012
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- 30 December 2011, pp 330-348
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Summary
A large diversity of alien plants is found in most mediterranean-type climate (MTC) regions and fire is sometimes closely linked to their ability to invade natural ecosystems. This is a concern because aliens often upset natural ecosystem processes, and thus are a major management concern. These five regions not only differ in their contributions of non-native plant species to other regions, but also vary in their susceptibility to invasion by alien species, something often referred to as a community's invasibility.
Fire is a key factor behind plant invasions into natural plant communities and particularly critical is the timing of propagule availability and characteristics of the fire regime. Fire also interacts with geology in dictating functional types that become pernicious invasive problems. For example, on coarse-textured low-fertility soils in two of the southern hemisphere MTC regions, shrubs and trees are among the most aggressive invasives, and are capable of invading seemingly undisturbed intact shrublands. However, on more fertile soils such as in California and Chile, grasses and other herbaceous species are bigger threats, but invasion typically requires disturbance and under some circumstances fire can effect type conversion from woody vegetation to alien-dominated grasslands.
11 - Plant Diversity and Fire
- from Section III - Comparative Ecology, Evolution and Management
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- Fire in Mediterranean Ecosystems
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- 05 January 2012
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- 30 December 2011, pp 310-329
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Summary
Mediterranean-type climate (MTC) regions are some of the most botanically diverse landscapes in the world (Table 11.1). They are among the 25 global hotspots of diversity in both richness of species and endemics (Myers et al. 2000). Occupying a bit more than 2% of the Earth's surface these landscapes hold 15–20% of the world's total vascular plants (Cowling et al. 1996; Rundel 2004). Between the five regions there is extraordinary variation in temporal and spatial patterns of vascular plant diversity and the relationship between fire and diversity is quite different across the five MTC ecosystems.
Differences between MTC regions are evident at many scales but one of the frequently noted differences is the regional species density or number of species per unit area. To put this in perspective we need to recognize that one of the commonly held generalizations about species diversity is that it increases with area (Fig. 11.1a,b). This species–area relationship is understandable since there are constraints on the number of individuals that can sustainably occupy a given area. Thus, as area increases, the probability of encountering more species increases. However, despite the observation that the number of species increases with increasing area is one of the few “laws” in ecology (Lomolino 2001), there are exceptions. Dissimilar environments often have very different species richness. Thus, this species–area relationship only approaches the status of a “law” when describing patterns in nested samples (Dunn & Loehl 1988); that is, samples of different size taken from within the boundaries of larger samples so that species from the smallest sample unit share environmental features with larger sample units (Box 11.1). There is no clearer demonstration of this than the species–area relationship observed for total regional diversity between the five MTC regions (Fig. 11.1c). The glaring lack of fit to an idealized species–area relationship (Fig. 11.1a) points up some of the important differences in diversity between these MTC regions. These patterns are the result of complex responses to subtle variations in climate, not so subtle variations in geology, and to their interaction with fire, as well as to phylogenetic and biogeographic histories.
13 - Fire Management of Mediterranean Landscapes
- from Section III - Comparative Ecology, Evolution and Management
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- Fire in Mediterranean Ecosystems
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- 05 January 2012
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- 30 December 2011, pp 349-387
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Summary
The hazardous mediterranean climate, highly flammable vegetation, and rugged terrain, all important elements of fire behavior, become problems only in the presence of people. People recreate and build homes in the mediterranean wildlands because of the delightful climate and will continue to do so as long as space is available. People start most fires, and their mere presence tends to warp fire suppression strategies because fire agencies must protect lives and property threatened by fires rather than “back off” and build fire lines around fire perimeters.
Carl C. Wilson (1979a), Chief of Division of Forest and Fire Research, USFS/Pacific Southwest Forest and Range Experiment StationHuman presence in mediterranean-type climate (MTC) regions has differed markedly in the length of human occupation; however, there are remarkable similarities in how early inhabitants altered fire regimes and how modern societies deal with the fire hazard. Here we draw on the history of human impacts outlined in the regional reviews (see Chapters 4–8), the problems created by nineteenth and twentieth century management practices, and conclude with twenty-first century problems and future options. As discussed throughout this book, MTC ecosystems are highly fire adapted but, as illustrated here, contemporary societies have not fully adapted to balancing fire hazard risk and resource needs on these landscapes.
Early Human Fire Use and Impacts
Fire has been a widely utilized management tool throughout the history of humankind (Pyne 1995). Early hunter–gatherers utilized fire to manage for plant and animal resources. Fire also played an important role in early domestication of crops as clearing off woody or other perennial vegetation would have required fire on many landscapes. With domestication of livestock it was an important tool for increasing forage.
2 - Fire and the Fire Regime Framework
- from Section I - Introduction
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- Fire in Mediterranean Ecosystems
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Summary
A global view of potential vs. actual vegetation distributions points to fire as a major driver of biome distribution and determinant of community structure (Bond et al. 2005). In ecological terms, fire acts much like an herbivore, consuming biomass and competing with biotic consumers for resources, and in this sense is an important part of trophic ecology (Bond & Keeley 2005). As in other competitive interactions, not only can fire competitively exclude herbivores by temporarily eliminating resources, but intensive grazing is known to exclude fire by consuming herbaceous ground fuels (Savage & Swetnam 1990). Coexistence is often enhanced by temporal separation of trophic niches, with herbivores grazing early in the spring on green herbaceous material that is unavailable for burning, whereas later in the season the remaining dry thatch is readily consumed by fire. In many respects fire is a more potent competitor because it is not limited by either toxins or protein deficiency and readily consumes dead woody biomass, but by contrast it is often limited by ignition sources and continuity of fuels.
Fire scientists have long symbolized the critical elements of fire in a triangle of fuel, oxygen and heat (Pyne et al. 1996). These are indeed necessary for fire ignition and propagation but are insufficient for predicting the global distribution of fire-prone ecosystems. The conditions both necessary and sufficient to explain the ecological distribution of fire activity can be summarized by four parameters: biomass, seasonality, ignitions and fuel structure (Fig. 2.1). In addition to biomass fuels to spread a fire there must be a dry season that converts potential fuels to available fuels. In mediterranean-type climate (MTC) ecosystems summer drought results in high fire hazard on an annual basis, in contrast to many temperate forests that are only periodically vulnerable to fire in response to decadal or longer oscillations in climate. Vegetation only burns when ignitions are present to initiate the combustion process and landscapes vary markedly in the potential for natural ignitions from lightning, and in the extent of anthropogenic ignition sources. However, understanding the ecosystem distribution of fire requires consideration of a fourth parameter, fuel structure, which is fundamental to recognizing how different fire regimes develop.
Contents
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- Fire in Mediterranean Ecosystems
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- 30 December 2011, pp v-vi
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Section II - Regional patterns
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- Fire in Mediterranean Ecosystems
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- 30 December 2011, pp 81-82
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Summary
Regional patterns
Mediterranean-type climates (MTC) comprise a diverse array of woody, herbaceous, and even succulent vegetation types in each of the five regions. Shrublands are universal across all MTC regions and have been the main focus of past comparative studies; however, woodlands and forests are of great interest in understanding drivers in these ecosystems. InSection IIwe examine in detail the intraregional patterns of variation in vegetation types and the ecological role fire plays in each of the five regions. We are concerned with the degree to which similar environments have converged on similar fire regimes and those factors responsible for divergence. A boiler-plate approach of topics covered in each region is not the appropriate metaphor here as each region presents very different problems associated with different landscape histories and fire responses. The nominate region, the Mediterranean Basin, has such an extraordinarily long and intensive human history that landscapes exist as a palimpsest with ecological patterns overriding signatures from earlier uses. Crown fires dominate all MTC regions but California is unique among these in having substantial forests of tall conifers prone to surface fire regimes, with different trajectories of trait evolution and fire management impacts. Central Chile exhibits patterns best interpreted as a fading fire regime, once quite evident but, like a dying star, it has been extinguished by the Late Miocene completion of the Andean uplift that now blocks ignition sources due to lightning. The Western Cape of South Africa is considered to have the climate and geology sufficient to support forests, but these are extremely limited and restricted to narrow refugia from fire. Southern Australia is phenomenal in that sclerophyllous-leaved mediterranean-type vegetation (MTV) covers much of the southern third of the continent, despite the lack of a MTC from middle Victoria to New South Wales in the southeastern corner of the continent.
6 - Fire in Chile
- from Section II - Regional patterns
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- Fire in Mediterranean Ecosystems
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- 30 December 2011, pp 150-167
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Summary
The Mediterranean-type Climate Region of Chile
The mediterranean-type climate (MTC) in Chile (Fig. 6.1) is distributed from La Serena (30° S; Región IV, see Appendix 6.1) in the north to Concepción (37° S; Región X) in the south. It is constrained to the west side of the Andean mountain range, although as the height of this range decreases in the south, a MTC is observed at least as far eastward as Bariloche, Argentina. Although a pattern of winter rains and summer droughts extends northward into the Atacama Desert, this area falls outside our definition of MTC because winter evaporation exceeds rainfall in these areas of extremely low precipitation. The northern border of the MTC region is the transition from desert communities to shrubby matorral, while the southern border corresponds to the point of transition from sclerophyll woodlands to Valdivian evergreen forests (Gajardo 1994; Amigo & Ramirez 1998; Rundel et al. 2007).
The landforms of central Chile can be divided into three north–south trending geomorphic zones (Fig. 6.1): the Coastal Cordillera, the Central Valley, and the high Andean Cordillera (Armesto et al. 2007). The Coastal Cordillera rises relatively sharply from the coast, with little extent of coastal terraces, and reaches elevations as high as 2222 m at Cerro Roble and 1880 m at Cerro Campana, which lie between Valparaíso (Región V) on the coast and Santiago (Región Metropolitana) at the base of the Andes. The Central Valley is a structural basin filled to great depth by sediments from the surrounding mountains. North of Santiago, spurs from the Andes extend west across the valley and connect with the Coastal Cordillera, separating individual river basins such as that of the Río Aconcagua (Región V). From Santiago to the south, however, the valley extends uninterrupted for a distance of 900 km to Puerto Montt (Región X), with typical elevations of 400–700 m. The Andean Cordillera marks the eastern boundary of the MTC zone of central Chile. It is the product of complex tectonic activity beginning in the Cretaceous (see Fig. 9.1), but with major uplift in the late Tertiary. Paleobotanical evidence suggests that the central Andes had not attained more than half their current elevation by 10 Ma (Gregory-Wodzicki 2000), but was close to the present height by the end of the Miocene (Reynolds et al. 1990). Elevations reach from 4000 m to nearly 7000 m. To the north of Santiago the Andes are largely composed of metamorphosed sedimentary rock, but a major volcanic zone extends from south of Santiago through the Lake District (Los Lagos Región X).
10 - Fire and the Origins of Mediterranean-type Vegetation
- from Section III - Comparative Ecology, Evolution and Management
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- Fire in Mediterranean Ecosystems
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- 30 December 2011, pp 275-309
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Summary
The mediterranean-type climate (MTC) is widely agreed to have been in place in all five MTC regions since at least the late Pliocene (see Fig. 9.1), ~2 Ma, with much of the contemporary mediterranean-type vegetation (MTV) present and contributing to a highly fire-prone environment. There is far less agreement on: (1) the timing of the origin of the MTC, (2) the timing of and factors responsible for the origins of MTV, and (3) the paleohistory of fire and extent to which it has played a role in the origins of MTV. Ample evidence exists to suggest a much earlier origin of MTC and MTV.
A widely held paradigm is that many of the woody sclerophylls that comprise MTV are much older than the Pliocene and thus have not adapted to contemporary fire-prone MTC conditions (Axelrod 1989; Herrera 1992; Verdú et al. 2003; Ackerly 2004a). Most of these have origins in the Tertiary Period of the early Cenozoic and are viewed as relictual taxa that represent evolutionary inertia and are present today merely by chance avoidance of random extinctions.
Fire in Mediterranean Ecosystems
- Ecology, Evolution and Management
- Jon E. Keeley, William J. Bond, Ross A. Bradstock, Juli G. Pausas, Philip W. Rundel
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- 05 January 2012
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- 30 December 2011
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Exploring the role of fire in each of the five Mediterranean-type climate ecosystems, this book offers a unique view of the evolution of fire-adapted traits and the role of fire in shaping Earth's ecosystems. Analyzing these geographically separate but ecologically convergent ecosystems provides key tools for understanding fire regime diversity and its role in the assembly and evolutionary convergence of ecosystems. Topics covered include regional patterns, the ecological role of wildfires, the evolution of species within those systems, and the ways in which societies have adapted to living in fire-prone environments. Outlining complex processes clearly and methodically, the discussion challenges the belief that climate and soils alone can explain the global distribution and assembly of plant communities. An ideal research tool for graduates and researchers, this study provides valuable insights into fire management and the requirements for regionally tailored approaches to fire management across the globe.
3 - Fire-related Plant Traits
- from Section I - Introduction
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- Fire in Mediterranean Ecosystems
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- 30 December 2011, pp 58-80
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Summary
As illustrated in Fig. 2.1 there are four environmental parameters that are necessary to determine the distribution of fire-prone ecosystems. However, they are insufficient to predict ecosystem responses to fire without a detailed understanding of the fire regime (see Fig. 2.7). Different fire regimes have very different potentials for recovery and place very different premiums on specific plant traits. For example, those traits contributing to the persistence of species in crown fire regimes will often be very different from those in surface fire regimes. In short, organisms are not adapted to fire per se, but rather to a particular fire regime. Plant traits that are adaptive in fire-prone environments are discussed here. The evolution of such traits and the extent to which they represent adaptations to fire are considered in Chapter 9.
Plant populations exhibit four modes of recovery following fire:
endogenous regeneration from resprouts or fire-triggered seedling recruitment,
delayed seedling recruitment from postfire resprout seed production,
delayed seedling recruitment from in situ surviving parent plants, or
colonization from unburned metapopulations.
Section III - Comparative Ecology, Evolution and Management
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- Fire in Mediterranean Ecosystems
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- 30 December 2011, pp 231-232
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Summary
Comparative Ecology, Evolution and Management
Here we utilize those points of convergence and divergence between mediterranean-type climate (MTC) ecosystems to develop a synthesis that reveals emergent properties not evident by study of any one region alone. Comparative study of plant traits, functional types and community responses to fire provides insight into selective factors driving the evolution and ecological assembly of fire-prone plant communities. Feedback processes are crucial to understanding evolution on such landscapes. Fire provides a challenge to understanding selective forces because, although inclusive fitness theory can explain fire-adaptive traits, such traits are dependent on community-level assembly that contributes to fire spread. MTC regions exhibit differences in climate and geology that have led to diverse fire environments, and account for many differences in trait evolution and community assembly. Humans have long been attracted to MTC regions but have not always adapted successfully to these fire-prone landscapes. Urban and peri-urban populations have been highly vulnerable to wildfires in some MTC regions, with differences in vulnerability between regions being due largely to innate differences in fuel loads of indigenous vegetation types and profound differences in population density.
8 - Fire in Southern Australia
- from Section II - Regional patterns
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- Fire in Mediterranean Ecosystems
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- 30 December 2011, pp 201-230
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Summary
The mediterranean-type climate (MTC) in Australia spans from the southwestern part of Western Australia to include much of South Australia and western Victoria (Fig. 8.1), which covers a longitudinal distance second only to the Mediterranean Basin MTC region. As in other MTC regions, the highly fire-prone evergreen sclerophyllous shrub and tree mediterranean-type vegetation (MTV) extends much further east and north into climatic zones that are not MTC. Australia, however, is distinctly unlike other MTC regions in that fire-prone MTV is extensive across the southern part of the continent and transcends climatic boundaries with relatively subtle changes in community structure and composition. Sclerophyllous MTV dominates both the MTC region of the southwestern corner of the continent as well as the southeastern corner under an aseasonal climate. Both regions share a common fire season of summer to early autumn (McArthur 1972); however, the MTC southwest has a potential fire season every summer whereas in the southeast it is tied to weather anomalies that occur once to several times a decade.
Mediterranean-type Vegetation
Within the southern Australian MTC zone (Fig. 8.1) evergreen sclerophyllous vegetation dominates. Such MTV is sometimes defined as shrub dominated (Specht 1979), and indeed large areas of sclerophyllous heaths (see Fig. 1.6f), shrublands (Fig. 8.2a) and mallee (Fig. 8.3) occur. However, woodlands and forests form integral parts of the MTC biome (Dell et al. 1989; Gill 1994), and thus MTV includes shrublands, woodlands and forests, and in southern Australia they dominate both in the MTC region and outside that climatic zone (Fig. 8.1). MTV is found across the southern temperate latitudes of Australia (Table 8.1) in an arc below about 30° latitude, accounting for dominant vegetation types in infertile habitats throughout temperate Australia. We specifically focus on the various heaths, shrublands and dry sclerophyll forests that constitute the most fire prone communities in these temperate landscapes. Although similar fire-prone MTV heathlands occur extensively within the tropics on the northern end of the continent (Keith et al. 2002; Russell-Smith & Stanton 2002), here we focus on the temperate MTV, but do consider broader relationships with other adjoining vegetation types (e.g. wet sclerophyll forests, rainforests, and various arid and semi-arid woodlands and shrublands).
References
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- 30 December 2011, pp 398-497
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7 - Fire in the Cape Region of South Africa
- from Section II - Regional patterns
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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Summary
South Africa's mediterranean-type climate (MTC) region is the smallest of the five MTC regions, centered in the southwestern corner of the Western Cape Province (Fig. 7.1). This Cape region is dominated by fynbos shrublands (see Fig. 1.6e) but this fynbos biome continues eastward far outside the MTC. The Cape region is unusual in that shrublands dominate under climate regimes that also support forests. Entire landscapes can support alternative ecosystem states. Even the semi-arid areas can support entirely different vegetation: fire-prone shrublands or fire-resistant broadleaf thickets. Perhaps more than any other MTC region, fire plays a central role in determining major vegetation patterns of winter rainfall regions of South Africa. Soils are also thought to be of major importance since much of the Cape's MTC region is on nutrient-poor sandy soils (see Fig. 1.5). A complex interplay between soils, fire and climate and, in the east, large mammal herbivory, determines boundaries of major biomes. The Cape Floristic Region is extremely rich in species with very high levels of endemism (Linder 2003). It is the world's richest temperate flora and is largely restricted to fire-prone ecosystems (Cowling et al. 1996; Linder 2003). So, contrary to the widely held popular belief that fires are an anthropogenic disturbance (e.g. Pillans 1924; Axelrod 1980), or merely incidental to this formation (Hopper 2009), a rich endemic flora has evolved in the Cape whose members are overwhelmingly fire dependent, implying a long history of natural fires as a selective force.
Major Vegetation Patterns
This chapter discusses fire regimes in the Cape region, what little is known of their determinants, and how they influence major vegetation patterns in the region. Though a large number of studies have explored plant responses to fire (reviewed by Bond 1997; Cowling et al. 1997a), these are heavily biased toward fynbos shrublands, the dominant vegetation cover of the region (Fig. 7.2). Fire responses of species belonging to other vegetation types are poorly known. Yet the existence of these other vegetation types is one of the central conundrums of the Cape region. It implies failure of climate alone to explain apparent convergence with other MTC regions (Chapter 1). For example, low shrublands would be expected in deserts replaced, as rainfall progressively increases, by taller shrublands, woodlands and then forests. But this is clearly not the case in the Cape region. The dominant fynbos vegetation shows very little variation in aboveground biomass from arid desert fringes (mean annual precipitation ~250 mm) to rain-drenched high-altitude heathlands (> 3000 mm) (Fig. 7.3). Yet across the entire rainfall gradient fynbos co-occurs with alternative ecosystems with much greater woody biomass. These broadleaf thickets and forests have an entirely different floristic and functional composition and often are restricted to isolated fire-protected refugia (Fig. 7.2; Taylor 1978; Kruger 1979; Cowling et al. 2005; Rebelo et al. 2006). The implication is that apparent convergence of shrubby fynbos growth forms with other MTC plant communities cannot be understood in terms of climate alone and that one needs to think in terms of the climate, fire, geology filter (see Fig. 1.4).
5 - Fire in California
- from Section II - Regional patterns
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- Fire in Mediterranean Ecosystems
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Summary
On the west coast of North America lies the state of California, USA (Fig. 5.1), the bulk of which is dominated by a mediterranean-type climate (MTC). Elevations range from sea level to over 4000 m. Mountain ranges are largely oriented north to south with a major valley between the coastal ranges and the interior Sierra Nevada range. In the rain shadow east of the interior mountain ranges the climate is more continental with much colder winters and increasing proportion of summer precipitation eastward. This easternmost part of the state has steppe climates in the northern portion and desert climates in the south. In Arizona and a few other parts of southwestern USA and northeastern Mexico are disjunct patches of sclerophyllous-leaved vegetation that closely resembles California MTC vegetation. These include evergreen shrublands, broadleaf woodlands and conifer forests and represent mediterranean-type vegetation (MTV) under non-MTCs. Further east at similar latitudes but under different climates are sclerophyll forests with many similarities to MTC conifer forests.
The California Floristic Province (Raven & Axelrod 1978) essentially circumscribes the MTC vegetation of North America and extends across the latitudinal range of the state. On the western slopes of the major mountain ranges is a rich diversity of vegetation types that change along the elevational gradient. Ascending the coastal mountains the main vegetation types sort out along gradients of decreasing aridity in the following order: grasslands, semi-deciduous woody sage scrub, evergreen chaparral shrublands, oak woodlands and conifer forests. A similar pattern is evident on the west side of the interior Sierra Nevada except for the absence of sage scrub. These vegetation types exhibit marked differences in fire regime and tolerance to disturbance tied to the different patterns of fuel structure resulting from changes in dominant growth forms along the elevational gradient. Along this gradient there is an interaction between fires and aridity such that lower fire frequency is required to displace shrubland associations with grasslands and other herbaceous vegetation on xeric than on mesic landscapes (Keeley 2002b). Consequently there are complex local mosaics due to differences in aspect and fire history (see Fig. 1.6c).
14 - Climate, Fire and Geology in the Convergence of Mediterranean-type Climate Ecosystems
- from Section III - Comparative Ecology, Evolution and Management
- Jon E. Keeley, United States Geological Survey, California, William J. Bond, University of Cape Town, Ross A. Bradstock, University of Wollongong, New South Wales, Juli G. Pausas, Consejo Superior de Investigaciones Cientificas, Madrid, Philip W. Rundel, University of California, Los Angeles
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- Fire in Mediterranean Ecosystems
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Integrating Climate, Fire and Geology in a Fire-prone World
Fire challenges the long-standing hegemony of ecology, biogeography and paleoecology that climate and soils are sufficient to explain the origin and distribution of plant species. In a world where half of the land surface is fire-prone (Krawchuk et al. 2009), understanding the past and predicting the future requires a close integration of climate, fire and geology. The dogma that fire is an anthropogenic phenomenon of little use in understanding paleoecology (Axelrod 1980, 1989), or merely incidental to vegetation development (Hopper 2009), is rapidly being replaced with a better understanding of paleofire's impact on land plant evolution (Scott 2000; Pausas & Keeley 2009). Attempts to model future global vegetation patterns have been demonstrated to be inadequate without including both natural and anthropogenic fire regimes (Bond et al. 2005).
Bond and Keeley (2005) outlined the conundrum posed by alternative explanations for the present distribution of vegetation and assembly of communities. Classical explanations have invoked resource-based mechanisms that are driven by climate and soils. There are ecosystems where resource-based mechanisms may be sufficient, but on many seasonally dry landscapes ecosystem processes such as fire play a major role in the organization and evolution of vegetation.